If you can only submit two, I’d go with your recent supervisor and your undergrad professor. Your supervisor is a must since you worked with her for four years she can speak to your professional growth and skills, which grad schools care a lot about, especially if you’ve been out of school for a while.
Even though the academic rec isn’t required, it still helps to have one and yours sounds solid, since she was your honors advisor and actually knows your work well.
The board member sounds cool, but since the connection is kinda old (high school internship) and not directly tied to the program you’re applying to, it probably won’t carry as much weight. Unless he’s writing something super personal and specific, it might come off more as a name-drop than anything meaningful.
So yeah, go with the two who know you best and can speak to what you’d bring to the program. Strong, relevant recs > fancy titles any day.